RAM Structural System Help

Multiple Story Unbraced Column

In some circumstances a physical column may extend unbraced through multiple levels, or be braced in only one direction at a level. Due to modeling constraints, or "real world" conditions, the physical column may need to be modeled as a single column at the same plan location on two or more stories. In RAM Concrete Column every column at every story is designed individually.

To maintain the reinforcing for the physical column that extends unbraced through multiple stories, the design forces for the full physical member should be applied for the design of the columns at each story. That is, for each individual column in an unbraced stack the column top and bottom forces are taken from the story at which the column is braced. The following figure illustrates this situation and also illustrates that in some circumstances the design moments about an axis, used for a column design at a specific story, may be taken from a column higher or lower in the unbraced column stack.

Column design moment notation

Given the moments shown in preceding figure about each axis for a two-story column stack, unbraced in the minor axis at the middle story, the moments listed in the following table will be used for column design.

Column Mx Top My Top Mx Bottom My Bottom
1 M xt1 M yt1 M xb1 M yb2
2 M xt2 M yt1 M xb2 M yb2